The present invention is a method and apparatus for receiving utility usage information over a plurality of telephone lines and more particularly a method and apparatus for receiving utility usage information in the form of alternating current representations from a plurality of interface devices, each interface device being coupled to both a distinct telephone line and to at least one utility monitoring device.
There have been other systems for receiving data from telephone lines such as the one described in U.S. Pat. No. Re. 26,331 to Dumont et al. Systems of the Dumont type use the telephone company's leakage testing system to call up individual meter installations. Once a meter installation is called up, it sends the meter information over the telephone line to a central telephone office, however, such systems have several disadvantages which make their systems undesirable for its intended use.
First, such systems require the use of a telephone company's leakage testing system to be operable and such leakage testing system can change, requiring an additional large investment in new equipment configured to the new leakage testing system. As well, not all telephone companies have the same type of leakage testing equipment, so that numerous configurations of the meter reading system must be devised to fit the numerous types of leakage testing equipment.
Second, such systems require a power supply, powered either from the power available at the meter installation site or from battery power for each of its meter installations. This requirement of a power supply makes such systems costly, difficult to service, and makes the systems prone to failures due to common power outages at the installation site.
Third, the Dumont invention requires synchronous data output on the telephone line. The synchronous output requires that the meter installations send additional sync data over the telephone line. In the event that either the sync data or synchronous meter data is momentarily interrupted by even a short noise pulse, which is quite common on telephone lines, the meter data will be lost.
Another system which has been used to send data over a telephone line is found in U.S. Pat. No. 3,922,490 to Pettis. The Pettis invention is a direct current system where several resistances are switched across tip and ring of the telephone line. The current drawn by the several different combinations of resistances connected to the telephone line are sensed at a central telephone office and any of several conditions are thus communicated. Typically, in the Pettis invention, the least significant digit pointer of a utility meter makes or breaks a switch depending on which half of its rotation the pointer is presently located. The making or breaking of the switch causes the resistance across the telephone line to change. This change is sensed at the central office and the cumulative count of changes in transition are totaled and the meter reading determined therefrom.
Of course, the Pettis invention, being a D.C. system, does not relate at all to the applicant's invention which is a method and apparatus for receiving data sent in the form of alternating current signals over a plurality of telephone lines.
U.S. Pat. No. 4,180,709 to Cosgrove et al also describes a system for enabling the monitoring of a plurality of resistances placed across the D.C. telephone line. As with U.S. Pat. No. 3,922,490, this invention relates only to monitorng data conducted by D.C. current changes and does not relate at all to the applicant's invention which monitors A.C. signals from the telephone line.
None of the art described has been able to continuously monitor each of a plurality of telephone lines with a low impedance to the A.C. data signals sent and received; none of the art described has been able to receive data from interface devices which are powered from the telephone line; none of the art described has been able to receive A.C. data which is asynchronous; and, none of the art described has sent utility usage information using dual-tone signals.